The present invention relates to the construction of a filter press and in particular to apparatus by which the filter plates are movable so that after opening the press the first filter plate is separated while the second and remaining filter plates are held in position.
Filter presses have been provided with means for sequentially moving the individual filter plates so as to expose them for cleaning or the like. In general, the filter plates are moved by chain drives, one chain drive being located on each side of the filter plates on either the press frame or on a frame above the plates. Means are arranged on the chain drives to hook onto a projection on the filter plates, thereby driving the latter. The chain drives travel round in a continuous manner and perform a reciprocating movement. On moving the filter plates, it frequently happens that not only the first filter plate is moved but, due to the sticking together of the individual plates, two or more such plates are moved, which is undesirable and constitutes a fault in the operation of the filter press. It has been known therefore to attempt to combine the apparatus for displacing the filter plates with means which seeks to ensure that only the first filter plate can be moved.
In a known construction, shown in British Pat. No. 1,441,316, a pivotable blocking member is arranged on each filter plate and engages with a rack, so that each plate is held in position in form-locked manner. The blocking member must be first released from the rack to displace the filter plate. This method of locking each individual filter plate constitute a costly solution and in addition the release of the locking mechanism is not reliable.
In another known construction shown in European patent application No. 0002101, a carriage with a spring-loaded latch or catch is arranged above the filter plates and engages in a rack rail. The carriage also carries a pivotable retaining lever securing in each case the subsequent filter plate, so that it cannot be moved in displacing the first filter plate. After moving a filter plate, the displacement mechanism must release first, the retaining lever and then secondly move the carriage sufficiently to ensure that the lever engages with respect to the subsequent second filter plate, thereby enabling the displacement mechanism to remove the first filter plate. Due to the need for an additional carriage and a rack, this solution is relatively costly.
According to another known construction shown in German DAS No. 1,295,517, two chain drives are arranged on either side of the filter plates. They serve merely to move the filter plates, one part of the plate being displaced by one chain drive and the other part thereof by the other chain drive. However, it is not possible to hold back the second filter plate.
The object of the present invention is to so further develop apparatus of the aforementioned type wherein both the displacement of the first filter plate and the retaining of the subsequent filter plate is possible with simple construction and minimum expenditure.